GREENER SYNTHESIS OF PYRANOPYRAZOLE DERIVATIVES CATALYZED BY CaO NANOPARTICLES

Abstract

We report on the development of a novel green synthetic protocol for the series of pyrano-pyrazole derivatives (5an) in a one-pot multi-component method using CaO nanoparticles as the heterogeneous catalyst. The CaO nanoparticles were synthesized by a greener route using an economic and efficient alternative i.e. papaya leaf extract and exhibited excellent catalytic activity, and this plant-mediated synthesis of CaO nanoparticles is a very promising area of research. CaO nanoparticles can be efficiently used in the synthesis of pyrano-pyrazoles and this catalytic approach can deliver the appropriate products in a rapid reaction time with a high yield (85–91%).The current protocol has various advantages, including a short reaction time, a high percent yield, a clean reaction, a simple separation technique, and a recoverable catalyst that retains its catalytic activity when utilized in subsequent reactions.Characterization of synthesized pyrano-pyrazole derivatives is done by IR, 1H and 13C NMR spectral data as well as HOMO-LUMO calculations.

Recent Synthesis of Mono‐ & Bis‐Pyranopyrazole Derivatives

“…(2023), for instance, reported on the synthesis of dihydropyrano[2,3‐c]pyrazoles via Knoevenagel‐Michael multiple reactions by using green catalyst Fe 3 O 4 @gC 3 N 4 for the reaction of aldehydes, phenylhydrazine, ethyl acetoacetate and malononitrile under 1 h reflux to achieve 97 % yield of product ( Route 1 ) [51] . This reaction has also been reported by using numerous catalysts such as 1,8‐diazabicyclo[5.4.0]‐undec‐7‐en‐8‐ium acetate ([DBU][Ac], [59] HMS/Pr−Rh‐Zr, [60] H 3 PO 4 /Al 2 O 3 , P 2 O 5 /SiO 2 , starch sulfuric acid, cellulose sulfuric acid, [61] thiourea dioxide (TUD), [62] PVC−EDA−CeIII, [63] citrus limon (lemon juice), [64] agave leaf ash extract, [65] piperidine, [66] sodium lactate, [67] NiWO 4 , [68] PBCMO‐amine, [69] CaO nanoparticles, [70] Fe 3 O 4 @chitosan‐tannic acid bionanocomposite, [71] FSiPSS nano‐catalyst, [72] nano ZrO 2 , [73] lactic acid : urea : NH 4 Cl, [74] H 4 [SiW 12 O 40 ], [75] NiFe 2 O 4 @SiO 2 −H 3 PW 12 O 40 (NFS−PWA), [76] Fe 3 O 4 @SiO 2 @CoSB, [77] PAN@melamine/Fe 3 O 4 nanocomposite, [78] isonicotinic acid, [79] nano‐[Fe‐PSMP]Cl 2 , [80] Fe 3 O 4 /MIP‐202‐H 4 WO 5 , [81] Zn(L‐proline) 2 , [82] baker's yeast, [83] solar radiation, [84] Cu‐DABP@Fe 3 O 4 /MCM‐41, [85] Fe 3 O 4 @NFC@Co(II), [86] PdO/Al‐SBA‐15, [87] (MnCoFe 2 O 4 @Niacin‐SO 3 H) + Cl − , [88] Zn‐CA‐MOFs [89] and Na 2 CaP 2 O 7 [90] …”